TRACE
            FOSSILS OF THE TAPEATS SANDSTONE


            
In the
            Payson Area, Northern Arizona

            
Lowermost
            member of the Tonto Group 

Updated 8/15/10
 
The Tapeats
            Sandstone is a lower middle Cambrian aged sedimentary sequence
            of conglomerates, coarse and fine sands down to nearly shale
            like facies. It represents a near shore to tidal flat deposit
            from 510 million years ago which covered the Payson area, Mogollon
            Rim and Grand Canyon areas in Arizona. Trace fossils are scarce,
            but when present give a unique window to a very ancient biome
            in which the dominant life forms were trilobites, a full range
            of extremely primitive arthropods, inarticulated brachs, hydrozoans,
            eocrinoids and other soft bodied forms that only were preserved
            as their traces on the sea bottom. The Tapeats was host to the
            same biota as the more famous Burgess Shale in Canada, Here in
            the Payson Area, we have two biogenic facies - the Skolithos
            facies and the Cruziana facies for trace fossils. Most of the
            trace fossils in the Payson area are various worm burrows and
            tubes, and we have as of yet never found a trilobite trackway
            here.

NOTE:  click the smaller thumbnails below for a larger version

Field Appearance
 
  Here is the outcrop at
            the East Verde River, just north of Payson. The sandstone layers
            sit on top of 1.8 billion year old Precambrian granite which
            decomposes to a coarse gravel through out the Payson area. Therefore
            there is a huge 1.2 Billion year disconformity here. Our house
            sits on the Tapeats as well, and while a few fossils are present,
            we have plenty of sedimentary structures. I always wanted to
            live near a beach...

Cruziana Facies - Deeper Water
 
 
            Diagram of the far from shore sand facies also found in the Payson
            area. We primarily have #8, Arenicolites fossils from this facies,
            which are a U tube worm burrow with no spreiten. (Former burrow
            position lines). We have also found a fossil not shown here,
            Bergauria - Sea anenome suction cup marks near the Verde River
            outcrops. We have yet to find Cruziana in Payson.
 
 
            Arenicolites, side view. Formerly called "Corrophiodes",
            this name has been reserved for an extant fish and is no longer
            used. Look carefully here, and you can see on the left side the
            U tube shape of the burrow.
 
 
            Arenicolites, Here are how most fossils are found, this is the
            very bottom of the U tube burrow, and looks like a curved slit
            in the mud. Many times the sandstones split like shales and show
            the layers that were below the surface as well.
 
 
            Arenicolites, surface view. Here are the paired holes that define
            what the mud surface would have looked like for this U tube worm
            burrow. The animal stayed in its burrow for its entire life and
            fed on the particles of food suspended in the water as it passed
            by.

 
            Arenicolites, as above found near out home near the Airport.
            Many U tube slits cover this specimen and shows the crowding
            that is encountered in many areas from this rich biome.
 
 
            Arenicolites, side view. Another view here of the actual U tube
            that the animal occupied during its filter feeding life style.
 
 
            Unknown Arthropod trackway. This was a fairly large animal, like
            a large crustacean or bottom crawling arthropod. We have never
            found anything like this ever.


Skolithos Facies - Near shore and Tidal Flats
 
 
            Diagram of the Skolithos facies. While I have yet to see Diplocraterion
            here, we have found both Skolithos and Monocraterion.
 
 
            Monocraterion. Straight vertical burrow, with funnel shaped opening.
            One can debate the purpose of the funnel, one possibility is
            the animal moved around in circles gathering food from the surface
            and rubbed a funnel in the top. Or perhaps the animal had feeding
            tentacles which needed a larger opening to emerge. The mystery
            of trace fossils!

 
 
            Monocraterion - close up. Found near the Airport.
 
 
            Skolithos Linearis - Side view of many small straight burrows
            that go into the sediment vertically. The picture below reveals
            the density throughout this rock.
 
 
            Skolithos Linearis - Top view. Same specimen as above. Every
            bump on the surface is the entrance to a vertical burrow. The
            density can be quite high in some areas. This was a worm with
            tentacles that fed on particles in the water currents by filter
            feeding.
 
 
            Skolithos Linearis -Larger animals. One of several species present
            in the Payson area.
 
 
            Skolithos Linearis - Side View same specimen.

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